Escapement mechanism



Sept 6, 1949. T. A. GUMMERSALL 2,481,213

ES CAPEMENT MECHANISM Filed Oct. 25, 1944 Patented Sept. 6, 1949 ESCAPEMENT MECHANISM Thomas Alfred Gummersall, Sunderland, England Application October 25, 1944, Serial No. .560,246 In Great Britain November 13, 1943 5 Claims. l

This invention relates to a silent lever escapement for clocks, Watches and the like.

According to my invention, `the pallet pins, instead of being securely fixed to the pallet arms, are rcsiliently attached thereto by mounting the pallet pins on the outer ends of at springs which are secured at their inner ends to the pallet arms in such a manner that the outer ends of the springs which carry the pallet pins spring away slightly from the face of the pallet arm, the face of which may be either flat or curved.

The locking face of the escape-wheel tooth engages .the departure pallet pin before the impulse imparted by the escape-wheel on the entrance pallet pin is completed, and conversely, and the spring which carries the pallet pin is pressed by the lockingl face against the face of the pallet arm, thus giving suicient rigidity to the pallet spring to transmit the imparted impulse from the escape-wheel. The tips of the escapewheel teeth are rounded-off .to prevent any vibratory noise occurring when the pallet pin disengages from the escape-wheel tooth. As the escape-wheel pushes aside the pallet pin, the latter carries with it the balance lever, which in turn gives a sufficient blow to the impulse pin of the balance wheel to send the latter with renewed energy on its vibration. To ensure silence in this action, a forked spring is secured at its base in thel fork of the balance lever, and this forked spring, while being sufciently resilient to act as a buffer to the impulse pin of the balance wheel, is strong enough to actuate the balance lever and unlock the escape wheel. Moreover, when the balance wheel impulse pin is in position to receive the blow from the balance lever, the impulse pin is at the base of the forked spring, where the spring is sufliciently strong to impart the necessary energy.

In order that the invention may be more clearly understood, reference is hereinafter made to the accompanying drawing which illustrates escapement mechanism according to one form of my invention.

The drawing illustrates an escape wheel I having teeth 2, each of which has a locking face 3 and an impulse face 4. The escape wheel rotates in a counterclockwise direction as indicated by the arrow. A balance or pallet lever 5 oscillates on an arbor 6, one end of the lever 5 being forked as usual to receive the impulse pin 'I of the balance Wheel 8. The other end of the lever 5 is fitted with a counter-balance 9. Oscillating in unison with the lever 5 on the arbor B is a pallet member I having pallet arms II and IIa, the

2 extremities of which are at all times clear of the teeth of the escapewheel.

According to my invention, and as shown on the drawing, the pallet member Il) carries a pair of thin at pallet springs I2 and I2a which are secured at their inner ends at I3 to the root or base of the pallet arms II. The Outer ends of the pallet springs I`2 and I2a carry pallet pins I4. and Illa adapted to engage the teeth of the escape-wheel.

A Y-shaped spring I5 is secured within the fork ofthe balance lever as shown, so that the base of the spring fork lies at the base of the fork or recess I 6 linthe end of the balance lever 5. The base leg I'IV of the forked spring I5 may be secured in a slotted block Illy carried by the lever 5.

In the position shown on the drawing, the entrance .pallet spring I2a carrying the pallet pin Illa is .pressed against the face 0f the pallet arm IIa bythe pressure of the locking face of the tooth2a of the escape-wheel. As the departure pallet spring I2 and kits pallet pin I4 come intoposition, the pallet pin I4 engages with the locking face 3 of the escape-wheel tooth 2b, before the'pallet pin I 4a rides off the impulse face 4 of the escape-Wheel tooth 2a, from which action the pallet member I0 and balance lever 5 receive an impulse which is imparted to the impulse pin 'I of the balance wheel 8 to oscillate the latter. This action is repeated in every movement. The high portion of the impulse face 4 of each escapewheel tooth is rounded off at I9 to prevent any vibratory noise due to the disengagement of the pallet pins I4 and I 4a, from the escape-wheel.

The forked spring I5 also ensures silence in action, this spring acting as a resilient buffer to the impulse pin l, but being strong enough to actuate the lever 5 and unlock the pallet pins from the teeth of the escape-wheel as the balance wheel oscillates in known manner. Also, when the impulse pin 'I is in position to receive the. blow imparted to it through the lever 5 from the pallet arm I I or I Ia, pallet pin I4 or Illa and the escapewheel tooth, the pin l is positioned in the base of the fork of the forked spring I5, which is suflciently strong to impart the necessary force to the pin 'I.

The spacing of the pallet springs I2 and I2a from one another, the spacing of the pallet arms II and Ila, and the spacing and width of the escape wheel teeth 2 are so related to one another that one pallet spring always engages one. of the locking faces of the escape wheel teeth before the impulse is completed, that is to say, before the other pallet spring is disengaged. Moreover, the

rounded parts of the higher extremities of the escape wheel teeth provide exit faces which are substantially concentric with the axis of the escape wheel, so that the exit face presents a surface which is substantially normal to the pallet spring as the latter leaves the impulse face, with the result that the exit face retards the movement of the pallet spring away from the extremity of its associated pallet arm. This retardation eliminates any vibration of the pallet spring.

I claim:

1. In an escapement mechanism, an escape wheel having peripheral teeth each of which presents a radial locking face and an inclined impulse face, a pallet member having rigid entrance and departure pallet arms extending therefrom toward said escape wheel and in the same plane as said escape wheel, the extremities of said pallet arms being clear of said teeth at all times, an arbor on which said pallet member is mounted, means for controlling oscillation of said pallet member about the axis of said arbor, a pair of flat pallet springs, each attached at its inner end to the root of one of the pallet arms and projecting at its outer end beyond the extremity of the pallet arm, each of said springs normally diverging away from the pallet arm at the side directed toward the locking faces of the said teeth, the extremities of said springs being so positioned relative to each other and to the teeth of the escape -wheel that the locking face of one tooth engages and presses one pallet spring toward its associated pallet arm while the impulse face of another tooth is still in engagement with the other pallet spring.

2. An escapement mechanism as claimed in fi claim l, having a pallet pin transversely fitted to the extremity of each pallet spring.

3. An escapement mechanism as claimed in claim l, having a rounded face at the higher extremity of each escape wheel tooth, said rounded face being substantially concentric with the axis of the wheel to prevent vibration of the pallet spring as it leaves the impulse face of the tooth and moves away from its associated pallet arm.

4. In an escapement mechanism, an escape wheel having peripheral teeth, each of which presents a radial locking face and an inclined impulse face, an oscillatory pallet member presenting entrance and departure pallet arms spaced from and in the same plane as said wheel, a spring pallet blade attached at its root to the inner end of each arm and projecting at its extremity beyond the pallet arm in a position diverging away from said arm toward the locking faces of the escape Wheel teeth, the spacing of said pallet arms and blades and the spacing and Width of the escape wheel teeth being such that each blade engages the locking face of a tooth before theimpulse face of one of the teeth has completed its impulse on the other blade.

5. An escapement mechanism as claimed in claim 4, having a rounded exit face at the higher extremity of each escape Wheel tooth, said exit face presenting a surface which is substantially normal to the pallet blade as the latter leaves the impulse face of the tooth, said exit face retarding the movement o the blade away from the extremity of the pallet arm so as to eliminate vibration.

THOMAS ALFRED GUMMERSALL.

REFERENCES CITED The following references are of record in the nie of this patent:

UNITED STATES PATENTS Number Name Date 1,867,947 Kohler July 19, 1932 1,895,666 Junghans Jan. 31, 1933 1,989,604 Poole Jan. 29, 1935 FOREIGN PATENTS Number Country Date 1,121 Great Britain Jan. 20, 1905 598,553 Germany June 13, 1934 786,656 France June 1'7, 1935 

